* Re: [syzbot] [btrfs?] possible deadlock in __btrfs_release_delayed_node (2)
[not found] <000000000000c826b605f748e7f2@google.com>
@ 2023-03-20 7:43 ` Hillf Danton
0 siblings, 0 replies; only message in thread
From: Hillf Danton @ 2023-03-20 7:43 UTC (permalink / raw)
To: Michal Hocko
Cc: Tetsuo Handa, Linus Torvalds, linux-mm, linux-kernel, syzbot,
syzkaller-bugs
On Sun, 19 Mar 2023 16:09:41 -0700
> syzbot found the following issue on:
>
> HEAD commit: 9c1bec9c0b08 Merge tag 'linux-kselftest-fixes-6.3-rc3' of ..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=163b8aecc80000
> kernel config: https://syzkaller.appspot.com/x/.config?x=dbab9019ad6fc418
> dashboard link: https://syzkaller.appspot.com/bug?extid=3ae9507d4e2431b56ff4
> compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/adcd3c9a01d5/disk-9c1bec9c.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/3f5bb295bb37/vmlinux-9c1bec9c.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/029aafd259b9/bzImage-9c1bec9c.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+3ae9507d4e2431b56ff4@syzkaller.appspotmail.com
>
> ======================================================
> WARNING: possible circular locking dependency detected
> 6.3.0-rc2-syzkaller-00050-g9c1bec9c0b08 #0 Not tainted
> ------------------------------------------------------
> syz-executor.1/26441 is trying to acquire lock:
> ffff8880286e5800 (&delayed_node->mutex){+.+.}-{3:3}, at: __btrfs_release_delayed_node+0x9a/0xaa0 fs/btrfs/delayed-inode.c:256
>
> but task is already holding lock:
> ffff8880592c24d8 (btrfs-root-01#2){++++}-{3:3}, at: __btrfs_tree_lock+0x3c/0x2a0 fs/btrfs/locking.c:197
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #3 (btrfs-root-01#2){++++}-{3:3}:
> lock_acquire+0x1e1/0x520 kernel/locking/lockdep.c:5669
> down_read_nested+0x40/0x60 kernel/locking/rwsem.c:1645
> __btrfs_tree_read_lock+0x2f/0x220 fs/btrfs/locking.c:135
> btrfs_tree_read_lock fs/btrfs/locking.c:141 [inline]
> btrfs_read_lock_root_node+0x292/0x3c0 fs/btrfs/locking.c:280
> btrfs_search_slot_get_root fs/btrfs/ctree.c:1774 [inline]
> btrfs_search_slot+0x571/0x2f70 fs/btrfs/ctree.c:2096
> btrfs_insert_empty_items fs/btrfs/ctree.c:4202 [inline]
> btrfs_insert_empty_item fs/btrfs/ctree.h:646 [inline]
> btrfs_insert_item+0x198/0x3a0 fs/btrfs/ctree.c:4231
> create_pending_snapshot+0xdef/0x28c0 fs/btrfs/transaction.c:1783
> create_pending_snapshots+0x195/0x1d0 fs/btrfs/transaction.c:1894
> btrfs_commit_transaction+0x1304/0x3440 fs/btrfs/transaction.c:2351
> create_snapshot+0x4a5/0x7e0 fs/btrfs/ioctl.c:844
> btrfs_mksubvol+0x5d0/0x750 fs/btrfs/ioctl.c:994
> btrfs_mksnapshot+0xb5/0xf0 fs/btrfs/ioctl.c:1040
> __btrfs_ioctl_snap_create+0x338/0x450 fs/btrfs/ioctl.c:1293
> btrfs_ioctl_snap_create+0x136/0x190 fs/btrfs/ioctl.c:1320
> btrfs_ioctl+0xbbc/0xd40
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:870 [inline]
> __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> -> #2 (btrfs-tree-01/7){+.+.}-{3:3}:
> lock_acquire+0x1e1/0x520 kernel/locking/lockdep.c:5669
> down_write_nested+0x3d/0x50 kernel/locking/rwsem.c:1689
> __btrfs_tree_lock+0x3c/0x2a0 fs/btrfs/locking.c:197
> btrfs_init_new_buffer fs/btrfs/extent-tree.c:4840 [inline]
> btrfs_alloc_tree_block+0x515/0x1800 fs/btrfs/extent-tree.c:4918
> btrfs_copy_root+0x345/0xcf0 fs/btrfs/ctree.c:327
> create_pending_snapshot+0xcc7/0x28c0 fs/btrfs/transaction.c:1768
> create_pending_snapshots+0x195/0x1d0 fs/btrfs/transaction.c:1894
> btrfs_commit_transaction+0x1304/0x3440 fs/btrfs/transaction.c:2351
> create_snapshot+0x4a5/0x7e0 fs/btrfs/ioctl.c:844
> btrfs_mksubvol+0x5d0/0x750 fs/btrfs/ioctl.c:994
> btrfs_mksnapshot+0xb5/0xf0 fs/btrfs/ioctl.c:1040
> __btrfs_ioctl_snap_create+0x338/0x450 fs/btrfs/ioctl.c:1293
> btrfs_ioctl_snap_create+0x136/0x190 fs/btrfs/ioctl.c:1320
> btrfs_ioctl+0xbbc/0xd40
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:870 [inline]
> __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> -> #1 (btrfs-tree-01){++++}-{3:3}:
> lock_acquire+0x1e1/0x520 kernel/locking/lockdep.c:5669
> down_read_nested+0x40/0x60 kernel/locking/rwsem.c:1645
> __btrfs_tree_read_lock+0x2f/0x220 fs/btrfs/locking.c:135
> btrfs_tree_read_lock fs/btrfs/locking.c:141 [inline]
> btrfs_read_lock_root_node+0x292/0x3c0 fs/btrfs/locking.c:280
> btrfs_search_slot_get_root fs/btrfs/ctree.c:1774 [inline]
> btrfs_search_slot+0x571/0x2f70 fs/btrfs/ctree.c:2096
> btrfs_insert_empty_items+0x9c/0x180 fs/btrfs/ctree.c:4202
> btrfs_insert_delayed_item fs/btrfs/delayed-inode.c:746 [inline]
> btrfs_insert_delayed_items fs/btrfs/delayed-inode.c:824 [inline]
> __btrfs_commit_inode_delayed_items+0xd53/0x2400 fs/btrfs/delayed-inode.c:1111
> __btrfs_run_delayed_items+0x1db/0x430 fs/btrfs/delayed-inode.c:1153
> flush_space+0x26d/0xe30 fs/btrfs/space-info.c:729
> btrfs_async_reclaim_metadata_space+0x106/0x350 fs/btrfs/space-info.c:1087
> process_one_work+0x8a0/0x10e0 kernel/workqueue.c:2390
> worker_thread+0xa63/0x1210 kernel/workqueue.c:2537
> kthread+0x270/0x300 kernel/kthread.c:376
> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
>
> -> #0 (&delayed_node->mutex){+.+.}-{3:3}:
> check_prev_add kernel/locking/lockdep.c:3098 [inline]
> check_prevs_add kernel/locking/lockdep.c:3217 [inline]
> validate_chain+0x166b/0x58e0 kernel/locking/lockdep.c:3832
> __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056
> lock_acquire+0x1e1/0x520 kernel/locking/lockdep.c:5669
> __mutex_lock_common+0x1d8/0x2530 kernel/locking/mutex.c:603
> __mutex_lock kernel/locking/mutex.c:747 [inline]
> mutex_lock_nested+0x1b/0x20 kernel/locking/mutex.c:799
> __btrfs_release_delayed_node+0x9a/0xaa0 fs/btrfs/delayed-inode.c:256
> btrfs_evict_inode+0x6f4/0x1090 fs/btrfs/inode.c:5398
> evict+0x2a4/0x620 fs/inode.c:665
> dispose_list fs/inode.c:698 [inline]
> prune_icache_sb+0x239/0x2e0 fs/inode.c:897
> super_cache_scan+0x376/0x480 fs/super.c:106
> do_shrink_slab+0x544/0xdb0 mm/vmscan.c:853
> shrink_slab_memcg mm/vmscan.c:922 [inline]
> shrink_slab+0x578/0x8c0 mm/vmscan.c:1001
> shrink_node_memcgs mm/vmscan.c:6439 [inline]
> shrink_node+0x1143/0x2730 mm/vmscan.c:6473
> shrink_zones mm/vmscan.c:6711 [inline]
> do_try_to_free_pages+0x67e/0x1900 mm/vmscan.c:6773
> try_to_free_mem_cgroup_pages+0x455/0xa50 mm/vmscan.c:7088
> reclaim_high+0x1e5/0x270 mm/memcontrol.c:2403
> mem_cgroup_handle_over_high+0x14a/0x2b0 mm/memcontrol.c:2588
Hi Michal
3) Anything other than defer handle_over_high to workqueue available in
order to avoid deadlock like this one, given GFP_NOFS?
> try_charge_memcg+0x13b5/0x16d0 mm/memcontrol.c:2826
> try_charge mm/memcontrol.c:2837 [inline]
> charge_memcg+0x11a/0x3f0 mm/memcontrol.c:6960
> __mem_cgroup_charge+0x27/0x80 mm/memcontrol.c:6981
> mem_cgroup_charge include/linux/memcontrol.h:678 [inline]
> __filemap_add_folio+0xe78/0x1b50 mm/filemap.c:857
> filemap_add_folio+0x121/0x580 mm/filemap.c:939
> __filemap_get_folio+0x7d5/0xe50 mm/filemap.c:1981
2) Add folio to pagecache.
> pagecache_get_page+0x2c/0x240 mm/folio-compat.c:99
> find_or_create_page include/linux/pagemap.h:632 [inline]
1) Allocate page with gfp = GFP_NOFS|__GFP_NOFAIL if no page in pagecache.
> alloc_extent_buffer+0x252/0xff0 fs/btrfs/extent_io.c:4044
> btrfs_init_new_buffer fs/btrfs/extent-tree.c:4799 [inline]
> btrfs_alloc_tree_block+0x2a0/0x1800 fs/btrfs/extent-tree.c:4918
> __btrfs_cow_block+0x470/0x1830 fs/btrfs/ctree.c:541
> btrfs_cow_block+0x403/0x780 fs/btrfs/ctree.c:696
> btrfs_search_slot+0xc89/0x2f70 fs/btrfs/ctree.c:2136
> del_balance_item fs/btrfs/volumes.c:3502 [inline]
> reset_balance_state+0x1e5/0x3a0 fs/btrfs/volumes.c:3577
> btrfs_balance+0xf17/0x1120 fs/btrfs/volumes.c:4415
> btrfs_ioctl_balance+0x493/0x7c0 fs/btrfs/ioctl.c:3592
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:870 [inline]
> __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> other info that might help us debug this:
>
> Chain exists of:
> &delayed_node->mutex --> btrfs-tree-01/7 --> btrfs-root-01#2
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(btrfs-root-01#2);
> lock(btrfs-tree-01/7);
> lock(btrfs-root-01#2);
> lock(&delayed_node->mutex);
>
> *** DEADLOCK ***
>
> 8 locks held by syz-executor.1/26441:
> #0: ffff88807eb2e460 (sb_writers#14){.+.+}-{0:0}, at: mnt_want_write_file+0x5e/0x1f0 fs/namespace.c:438
> #1: ffff88807c1cd440 (&fs_info->balance_mutex){+.+.}-{3:3}, at: btrfs_balance+0xbeb/0x1120 fs/btrfs/volumes.c:4381
> #2: ffff88807eb2e650 (sb_internal#2){.+.+}-{0:0}, at: del_balance_item fs/btrfs/volumes.c:3492 [inline]
> #2: ffff88807eb2e650 (sb_internal#2){.+.+}-{0:0}, at: reset_balance_state+0x12e/0x3a0 fs/btrfs/volumes.c:3577
> #3: ffff88807c1ce390 (btrfs_trans_num_writers){++++}-{0:0}, at: spin_unlock include/linux/spinlock.h:390 [inline]
> #3: ffff88807c1ce390 (btrfs_trans_num_writers){++++}-{0:0}, at: join_transaction+0xbfd/0xe80 fs/btrfs/transaction.c:287
> #4: ffff88807c1ce3b8 (btrfs_trans_num_extwriters){++++}-{0:0}, at: join_transaction+0xc28/0xe80 fs/btrfs/transaction.c:288
> #5: ffff8880592c24d8 (btrfs-root-01#2){++++}-{3:3}, at: __btrfs_tree_lock+0x3c/0x2a0 fs/btrfs/locking.c:197
> #6: ffffffff8cfd4690 (shrinker_rwsem){++++}-{3:3}, at: shrink_slab_memcg mm/vmscan.c:895 [inline]
> #6: ffffffff8cfd4690 (shrinker_rwsem){++++}-{3:3}, at: shrink_slab+0x2dc/0x8c0 mm/vmscan.c:1001
> #7: ffff88807eb2e0e0 (&type->s_umount_key#77){++++}-{3:3}, at: trylock_super fs/super.c:414 [inline]
> #7: ffff88807eb2e0e0 (&type->s_umount_key#77){++++}-{3:3}, at: super_cache_scan+0x77/0x480 fs/super.c:79
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2023-03-20 7:43 ` [syzbot] [btrfs?] possible deadlock in __btrfs_release_delayed_node (2) Hillf Danton
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